1. Field of the Invention
The present invention relates to a camera capable of automatic focusing (AF) by a contrast method.
2. Description of Related Art
In this field of the art, as one of ways of automatic focus (AF) adjustment for use in a camera, there is a so-called contrast method. According to this method, an object is picked up by an imaging element such as CCD or so and an in-focus position is determined by using an imaging signal in a focus detection area. More specifically, a component of a given spatial frequency band is extracted from an imaging signal within a given focus detection area by a band pass filter and by integrating a component's absolute value, focus evaluation value is calculated. This focus evaluation value is an amount that corresponds to a contrast of a focus detection area and the higher a contrast is, the higher the value is. In view of the fact that the closer a focus lens is to an in-focus position, the higher a contrast of an object becomes, detects a position showing a peak value of focus evaluation value is detected and judged to be an in-focus position and then a focusing optical system is driven to the in-focus position.
As one of ways to detect a peak value position, a focus lens is driven to scan from a point at infinity away to a point at a closest distance away or vice-versa and while scanning, every time a focus lens moves by a given movement pitch, each focus evaluation value is calculated respectively and each calculated value is also memorized respectively and then, by evaluating a plurality of memorized each focus evaluation value, a peak value position is obtained (a scan method).